We are using molecular biology, microbiology and protein engineering to develop a new type of preventative for HIV infection. Our approach uses live microbes that secrete anti-HIV peptides onto the mucosal surfaces where sexual transmission of HIV occurs. We have demonstrated the feasibility of this live microbicide approach by genetically engineering commensal strains of both rectal and vaginal bacteria to secrete high levels of HIV fusion inhibitor proteins both in vitro and in vivo. This novel live microbial microbicide is currently being tested in nonhuman primates. The primate system is also being used to analyze the interrelationships between vaginal microflora, the menstrual cycle, and the innate immune system. A new project involves the development of novel high definition real time video methods to monitoring HIV infection and growth in tissue explants. These will provide a novel assay system for the efficacy of microbicides